In recent years, display devices such as liquid crystal display (LCD) and the like, and input devices such as touch panel and the like, which are used in combination with the above-mentioned display devices, have been widely used in various fields. For production of such display devices and input devices and the like, transparent adhesive sheets and transparent curable resin layers, which cure with heat or UV (e.g., curable resins such as acrylic resin, urethane acrylate, silicone and the like, which cure with heat or UV) are used to adhere optical elements. For example, a transparent adhesive sheet is used to adhere a transparent protection plate, a touch panel, a lens and the like to a liquid crystal panel (e.g., JP-A-2003-238915, JP-A-2003-342542, JP-A-2004-231723).
However, when an optical element is adhered to a liquid crystal panel via a transparent adhesive sheet, adhesion may be repeatedly tried when inconvenience occurs such as inaccurate positioning of the liquid crystal panel and the optical element, air void involved between them that lowers the visibility of the display and the like. Therefore, the Applicants of the present application proposed a polyoxyalkylene adhesive sheet as a transparent adhesive sheet superior in reseparatability, which can be stuck again (JP-A-2008-266473).
The Applicant of the present application also proposed a method of separating two optical elements adhered to each other via a pressure-sensitive adhesive sheet, without allowing breakage or crack in them (JP-A-2010-121134). In this method, two optical elements (e.g., liquid crystal panel and transparent protection plate) adhered to each other via a pressure-sensitive adhesive sheet or a curable resin layer are separated by relatively moving the two optical elements in parallel to each other to cause a shear stress leading to the rupture of the pressure-sensitive adhesive sheet or curable resin layer.